Romney has been getting daily intel briefings. He cannot legally discuss classified info, unless it’s already been leaked. That’s why some of his surrogates are talking about it, they don’t get the briefings. Issa and Chaffetz haven’t been talking about the ‘annex’ issue. They can’t do so publicly.
He did let others bring it up, like at the rally last night where Guiliani and others slammed Obama over it. But they can answer questions from the press; for Romney to put himself "out there" to respond to questions could prove a little awkward.
Speaking of awkward responses, in an article discussing Hillary Clinton's role in Benghazi-gate our esteemed Secretary of State offered this pearl of wisdom:
"I think intelligence is very hard to do."
NS Sherlock!